1. Field of the Invention
The present invention concerns rigid cellular products and methods of preparation therefor. More particularly, the present invention concerns rigid isocyanurate cellular products or foams and methods of preparation therefor. Even more particularly, the present invention concerns furan-modified isocyanurate rigid foams and methods of preparation therefor.
2. Prior Art
Recently there has been described the preparation of carbon foams from polyurethane-polyfurfuryl alcohol cellular products. See, Theoni et al, J. Cell Plas., 1971, p. 294-301. The foams produced hereby were found not to undergo fusion under intense heats, but, rather, retained their structural integrity, even in the carbonized state. This is attributable to the structure derived from the furan polymer in the preparation of the product.
Unmodified furan polymers are known to be chemically inert, heat resistant, infusible materials in the completely polymerized state. On ignition, the polymers char and retain their cellular structural integrity. The properties of furan resins are more completely discussed by Seigfried, "FURAN POLYMERS", Encyclopedia of Polymer Sci & Tech., Ed. N. M. Bikales, v. 7, 1967, pp. 432-435; Dunlop and Peters, "THE FURANS", Am. Chem. Soc. Monograph 119, Reinhold Pub. Corp., New York, 1953, pp. 774-790, and U.S. Pat. No. 3,681,286.
Other background art can be found in U.S. Pat. Nos. 3,538,035; 3,168,489, as well as U.S. Pat. No. 3,509,103 which teaches furan-modified polyurethane from furfuryl alcohol blocked polyisocyanates.
While isocyanurate foams have enjoyed relative popularity in recent times, there has been a dearth of art directed to capturing the advantages of other organic groups by incorporating same therewithin. U.S. Pat. No. 3,793,236 teaches oxazolidone-modified polyisocyanurate foams which incorporate oxazolidone groups into such foams. However, heretofore, there has not been taught the advantages accruing to the incorporation of furan or furan derivatives into isocyanurate rigid foams. It is to this to which the present invention is directed.